Electrical apparatus and its operation



Aug. 24, 1943. o. MINTON ELECTRICAL APPARATUS AND ITS OPERATION FiledOct. 12, 1939 INVENTOR 0605M /1//v7'0/v BY l '1 I ATTORNEY Patented Aug.24, 1943 nmc'rmcAL macros nan ITS OPERATE??? Ogden Minton, Greenwich,Conn,

osclgnor to Ele- Li-Po, Inc., Greenwich, @ctnm, a corporation ofConnecticut Application October 12,19353 genial No. 299,077 Claims. (CLmil 118) This invention relates to electricity and more particularlypertains to electrical apparatus and operation.

In small electrical power plants, it frequently happens that one or moreelectric motors of considerable capacity must be operated intermittent-1:7. The starting of any one of such motors reuires an inrush of currentin the power line 4 Heretofore in electrical power plants of thischaracter, it has been necessary to install a main generator which is ofsuflicient capacity to start the motors that may be thrown across theline intermittently. This arrangement makes it necessary for a largecapacity generator to be operating under a comparatively light runningload. It is well known that generators operate at very lowefficiencyunless they are operated at some substantial part of their ratedcapacity. For example, this efficiency may fall lower than twenty-fivepercent at light loads, whereas it may be as high as ninety percent atloads of seventy-five percent (75%) of capacity. Accordingly, in priorpractice, generators in power plants of the type mentioned operate atvery low efiiciencies normally, and only-perform at reasonably higheificiencies during the short intervals of time required to start theone or more motors in the plant.

The present invention overcomes this disadvantage and provides anelectrical power plant of the type referred to, which has a generator ofsuilicient capacity to carry the running load of the plant, and isprovided with other means for starting the one or more motors oroperating other current consuming devices from time to time. Theinvention makes it possible .to operate the generator at a higheiliciency at all times, and to start the motors and operate otherdevices in circuit automatically.

The invention will be understood from the following description whenconsidered in connection with the accompanying drawing forming a partthereof, and in which:

Fig. 1 is an elevational view, showing more or less diagrammatically, anelectrical power plant embodying the invention, and

my. is a wiring diagram of the power plant to the drawing, referencecharacter an internal combustion engine of of suitable form, a flywheelll mounted on engine shaft which drives a three-phase alternatingcurrent generator i2 having a capacity oi" 2i) law for example. Theeizciter id for generate" is driven from the generator shaft bystd-table means such as the chain sprocket arrangement it. Analternating current gcner atcr it having a capacity of ii) law. forexample, coupled mechanically directly to the shaft of generator 92 bymeans or a coupling which is adjustable and is so adjusted that thegenerators it and it are always in phas with each other. Generator ithas an Exciter ll and a flywheel 58 mounted on its armature shaft. Anelectric motor ill, for example a 16 law. motor, drives some device notshown, such as a refrigerating compressor, through a hell; running overa pulley ii on one end of its shaft. In the form shown, the starting andstopping of electric motor it is controlled by a thermostat Acentrifugal switch 22 ct any suitable form, is mounted on and is drivenby motor i9, and is so arranged that it breaks an electrical circuitwhen the motor it] comes up to full speed.

Motor i9 is com ected int from, the main circuit ri nich the senoratorit? is cont-cruelly conic. ted by a normally open switch it which closeda solenoid 25. The energization of the soleno l is controlled by thethermostat it, as shown, which is connected across the main circuitThermostat 28 also controls the energizatic-n of a solenoid 21 whichcloses a normally open switch which connects generator i5 with the line23. A normally closed switch 28 which is in electrical circuit with andis controlled by centrifugal switch 22, controls the circuit connectingthe thermostat and the winding of the solenoid 2?. A lighting load 3| of10 k.w. for example, is connected in the main circuit. The excitercircuits and the voltage disconnected regulator circuits have beenomitted for the sake of simplicity, since they form no part of theinrention.

In operation, the engine it is started and is kept running at somepredetermined speed by a governor, and drives the generators. i3 and i5.Flywheel i8 is made of adequate weight and. diameter to store sufilclentenergy to prevent a falling oil in speed of the power plant over asufficiently long period 0! time to permit the starting of motor I8.Assume that lighting load operating, and with the 10 k.w. lighting loadon the line, there will be available 50 k.w. capacity of current tostart the motor I9, which is ample to efiect the starting of this motor.The flywheel l8 has sufiicient energy stored in it to keep the speed ofthe power plant from dropping too much during the time the motor I9 isgetting up to full speed. Ordinarily, it will require from 3 to 7seconds for motor I9 to attain its normal speed and when this speed isreached, the centrifugal switch 22 operates to open switch 29 and tobreak the circuit to the coil of solenoid 27, opens switch 28 and cutsgenerator I ofi the line. Switch 24 will remain closed and motor I9 willcontinue to run until the thermostat 26 breaks the circuit to the coilof solenoid 25 and opens switch 25. Then motor I9 will stop, centrifugalswitch 22 will close switch 29, and the power plant is ready for anotherstarting of motor I9.

From the foregoing description, it will be perceived that the generatorI5 only comes on the line when some abnormally large load, such asresults from the starting of motor I9, is thrown on the line. Theremainder of the time the generator I5 runs idle and acts like aflywheel. Hence the generator I2 will operate at all times at a highefiiciency and the motor i9 maybe started and stopped at will, withoutinterfering with the operation of the generator l2.

Under some circumstances, the flywheel I 8 may be omitted because. theengine flywheel II, and the generators I2 and I5 may provide an adequateflywheel eifect. In the example given, the engine I0 need have acapacity only sufiicient to carry the load of 20 k. w. made up of thelighting load 30 of k. -w. and the motor load l9 of 10 k. w. Inconsequence, it will be understoood that both a mechanical and anelectrical flywheel effect is produced by utilizing this invention.

If desired, a switch similar to the switch 28 and similarly operated,may be used to throw the exciter current ofi and on. Or, the excitercurrent may be maintained at all times.

The capacities mentioned herein for the several parts of the systemdisclosed, are to be considered as illustrative only, and are not to betaken as limiting the scope of the invention in any way. Obviously, thesize and capacity of the individual parts of the system may be varied asdesired, within the limits of the invention.

Since changes may be made in the form of the invention selected forillustration and in the several parts thereof, and in their location inthe system without departing from the principles of the invention,itwill be understood that the invention is not to be limited exceptingby the scope of the appended claims.

What is claimed is:

1. An electrical power plant comprising an alternating currentgenerator, a current consuming device connected in circuit with thegenerator, an electric motor, the generator having a capacity suificientto operate said current consuming device and motor but insufiicient tostart said motor, a second alternating current generator having itsarmature shaft mechanically coupled to the armature shaft of the firstgenerator in such manner that the two generators are al- .ways in phasewith each other and having a capacity suflicient to start the motor inconjunction with the first generator, switch means responsive to acondition requiring the starting of said motor for connecting the motorin circuit with both saidgenerators, and speed responsive switch meansfor disconnecting the second generator from said motor when the motorhas been started.

2. An electrical power plant comprising an alternating currentgenerator, a current consuming device connected in circuit with thegenerator, an electric motor, the generator having a capacity sutficientto operate said current consuming device and motor but insuflicient tostart said motor, a second alternating current generator having itsarmature shaft mechanically coupled to the armature shaft of the firstgenerator in such manner that the two generators arealways in phase witheach other and having a capacity sufiicient to start the motor inconjunction with the first generator, switch means responsive toconditions requiring the starting and stopping of said motor forconnecting the motor in circuit with both said generators when the motoris to be started and for disconnecting the motor from the firstgenerator when operation of the motor is not required, and speedresponsive switch means for disconnecting the seond generator from saidmotor when the motor has been started.

3. An electrical power plant comprising an alternating currentgenerator, a current consuming device connected in circuit with thegenerator, an electric motor, the generator having a capacity suflioientto operate said current consuming device and motor but insufiicient tostart said motor, a second alternating current generator having itsarmature shaft mechanically coupled to the armature shaft of the firstgenerator in such manner that the two generators are always in phasewith each other and having a capacity sufiicient to start the motor inconjunction with the first generator, a flywheel on the armature shaftof the second generator, switch means responsive to a conditionrequiring the starting of said motor for connecting the motor in circuitwith both said generators, and speed responsive switch means fordisconnecting the second generator from said motor when the motor hasbeen started.

4. An'electrical power plant comprising an al-- ternating currentgenerator, a current consuming device connected in circuit with thegenerator, an electric motor, the generator having a capacity sufficientto operate said current consuming device and motor but insufiicient tostart said motor, a second alternating current generator having itsarmature shaft mechanically coupled to the armature shaft of the firstgenerator in such manner that the two generators are always in phasewith each other and having a capacity sufficient to start the motor inconjunction with the first generator, an internal combustion engine fordriving said generators, switch I means responsive to a conditionrequiring the start operation or said translating device when operatingin conjunction with the first generator, switch means responsive to acondition requiring the starting 01' the operation of said translatingdevice for connecting said translating device in circuit with both saidgenerators, and switch means automatically responsive to the conditionsoccurring during operation oi said translating device for disconnectingthe second generator from the translating device when the device hasbeen started.

OGDEN MINTON.

